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This is my nutshell guide to growing Oca. Follow these tips and, given a good variety and fair soil, you should be able to achieve about a kilogram of tubers from each plant.

In order of importance:

Don't grow Oca in an area prone to early frost. Tubers only start to form after the equinox (about 22nd Sept), so if you commonly experience frost in September or October, the crop will be light or non-existent unless you provide crop protection. Most sources describe November or December as the normal harvest time, but for a big harvest, try to keep the plants frost-free until mid December.

Wait! After the killing frost, wait for 14 days (according to most sources), or possibly 21+ days (somewhat supported by my results), before harvesting. This gives time for the plant biology to finish turning plant tissue (some of which is hidden below ground) into tubers. Waiting a few extra days can have a noticeable effect on tuber yield (subject to Tip 3).

If hard weather is forecast between the killing frost, and the prescribed harvest date, consider lifting early, earthing-up, or adding physical protection/insulation. If you don't do this, you may loose some of the crop to penetrating frost (which makes tubers unusable), or foraging rodents. This is especially important if tubers are showing at the soil surface — crowded swelling tubers can push themselves up during the final weeks.

Water thoroughly during dry periods in late Summer and Autumn. The plants develop a lot of foliage during this period and moist conditions help to support it. Mulching in early Summer conserves moisture, and this same mulch will help to insulate the tubers from frost later in the year.

Give them root space, sprawl space, and light - especially in late Summer.

This is a really helpful clear guide. It's only a few hours since I discovered Oca via your blog (and then weirdly found it 2 other places, having never heard of it before) and I'm definitely sold on trying it out. Very grateful to you and your blog for sharing your experience.

It's probably a risk in my normally cold Scottish garden but worth a try for what sounds like the type of flavour I love. Wish I'd planted some earlier in the year because this winter has has so little frost (esp compared to last year) that if I'd had it in I'm sure I'd have had a bumper crop.

Fantastic to find that the word is finally getting out in the UK about Oca. In my native New Zealand it's known as 'NZ yams' and readily available in supermarkets. I've never understood why such a delicious food isn't a global one!

Growing the last couple of years in the north of ireland-very tasty crop-working out some of the salady and the cooking recipes for it-hoping for a good crop this winter.In the hard winter of 2010 earthed up a lot and left most in ground-that set me up for a lot of "seed" oca for 2011 and 2012...

I am in Los Angeles, California. We are not familiar frost... December temperature is about high 20 degrees Celsious and 9 degrees lowest. Will December be best time for harvest? or should I wait for January? I would like your opinion because this is my first year growing oca. Or how should I determine it is time to harvest, since there is no frost? Thank you very much!

I would expect the plants to die back even if there is no frost. When that happens will probably depend on the variety and your day length, but it will be a clear indicator that optimum harvest date is imminent.

Hi Anonymous, not usually, but I often add compost and/or organic matter to the soil surface around the crop as it grows. 'Hilling' or earthing up is a good method if weed competition is likely to be a problem.

Thanks, Ian! My ocas seem to be doing well but i think i spaced them too tight and i am thinking of expanding the bed in hopes of a larger crop. So far, i am following your steps in planting with tomatoes and it seems to be working well(no tomatoes yet/flowers dropped). I would like to Ullucos next season along with better varieties of Ocas. In USA, there is not much variety of Ocas yet. thank you for your wonderful blog!!! it helped much very much.